Introduction to Kubernetes

What is Kubernetes?

The official definition: Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, networking, and management of containerized applications.

The simpler version: Kubernetes is a manager for your containers. Docker creates containers; Kubernetes manages them. Running docker run nginx gives you one container on one machine — but Docker has no answer for who keeps thousands of containers healthy across hundreds of servers. That's Kubernetes' job.

A useful analogy is a large hotel: 500 rooms, 300 employees, 1,000 guests. The owner can't personally assign rooms, handle complaints, replace staff, and maintain services — so they hire a manager who does all of it. Docker builds the rooms; Kubernetes is the manager who runs the hotel.

Without Kubernetes              With Kubernetes

Docker                          Developer
  ├── Container                     │ deploys the application
  ├── Container                     ▼
  ├── Container                 Kubernetes
  ├── Container                  ┌───┼───┐
  └── Container                  ▼   ▼   ▼
                             Container Container Container
Everything managed manually   Everything managed automatically

Why the Name?

"Kubernetes" comes from the Greek word for helmsman — the person who steers a ship. That's also why the logo is a ship's steering wheel: Kubernetes steers your applications. You'll often see it abbreviated K8s (K, then 8 letters, then s).

A Short History

Kubernetes grew out of Borg, Google's internal system for scheduling millions of containers a week across its data centers. Google open-sourced the ideas as Kubernetes in 2014 and later donated the project to the Cloud Native Computing Foundation (CNCF), which maintains it today.

Every major cloud offers it as a managed service — Google Cloud, AWS, Azure, Oracle Cloud, IBM Cloud, DigitalOcean — and it runs production workloads at Netflix, Spotify, Airbnb, Uber, LinkedIn, Pinterest, Adobe, PayPal, and Shopify. When you stream a movie tonight, there's a good chance a Kubernetes cluster is serving it.

What Can Kubernetes Do?

• Deploy applications from declarative specs
• Self-heal — detect a crashed container and replace it automatically
• Scale applications up and down with load
• Load balance traffic across container replicas
• Roll out new versions with zero downtime, and roll back failed ones
• Manage networking, storage, and service discovery between components

The one-line memory trick worth keeping for the rest of this course:

Docker creates containers.
Kubernetes manages containers.

Setting up a Local Cluster

# Install kubectl
brew install kubectl
 
# Option 1: kind (Kubernetes in Docker) — recommended for CI
brew install kind
kind create cluster --name dev
 
# Option 2: minikube — recommended for learning
brew install minikube
minikube start
 
# Option 3: Docker Desktop
# Enable Kubernetes in Docker Desktop → Settings → Kubernetes
 
# Verify
kubectl cluster-info
kubectl get nodes

kubectl Essentials

kubectl is the CLI you'll use for everything. These commands will make complete sense by the end of Day 1 — skim them now, and come back as a reference:

# Get resources
kubectl get pods
kubectl get pods -o wide          # show node + IP
kubectl get pods --watch          # stream updates
kubectl get deployments
kubectl get services
 
# Describe (human-readable detail + events)
kubectl describe pod my-pod
 
# Logs
kubectl logs my-pod
kubectl logs -f my-pod            # follow
 
# Execute into a pod
kubectl exec -it my-pod -- sh
 
# Apply/delete config
kubectl apply -f deployment.yaml
kubectl delete pod nginx
 
# Port forward for local testing
kubectl port-forward pod/my-pod 3000:3000
kubectl port-forward svc/my-service 8080:80